The sync() system call forces a
write of dirty (modified) buffers in the block buffer cache out to
disk. The kernel keeps this information in core to reduce the
number of disk I/O transfers required by the system. As information
in the cache is lost after a system crash, a sync() system
call is issued frequently by the user process syncer(4) (about
every 30 seconds).

The fsync(2) system call
may be used to synchronize individual file descriptor
attributes.

SEE ALSO

fsync(2), syncer(4), sync(8)

HISTORY

The sync() function appeared in
Version 6 AT&T UNIX.

BUGS

The sync() system call may return
before the buffers are completely flushed.